As quantitative data become available for a particular form or function in the nervous system, it is advisable to attempt to assimilate the information in a comprehensive model of the underlying mechanisms and their interactions. This project consists in the development of such models and the necessary analytical and mathematical techniques for their implementation and testing in several areas of experimental investigation carried out by LNLC members and in other laboratories. Drs. Marks, Burke, and Ulfhake, guided by the discovery described in last year's Annual Report, that for motoneuronal dendrites, local dendritic diameter largely determines the rate of branching, terminating, and tapering, showed that (a) these rules, augmented by the empirical distributions of daughter branch diameter, satisfactorily predict the branch length distributions of dendritic trees of alpha and gamma motoneurons to the gastrocnemius and soleus muscle, using the empirical branching and tapering rates of these four neuron types; (b) the meanderings of the dendrites between branch can be described as random walk constrained to have a fractal dimension of about 1.2; (c) the membrane area beyond an branch obeys a simple law implied by the rules; and (d) to fit real neurons, the rules must explicitly constrain the growth beyond any branch point not to exceed that allowed by the diameters of the parent branches.